Probiotic yogurt works differently than expected

Probiotic yoghurt does not promote bacterial colonization

27/10/2011

According to a US study by nutritionists, probiotic yogurt promotes no colonization of beneficial bacteria in the gut. Also, the composition of the intestinal flora is not changed by the yoghurt, as reported medially again and again. However, the probiotic agents can positively alter the behavior of the gut microbes. However, the mode of action only lasts on daily and regular consumption. The study results were previously in the journal „Science Translational Medicine“ released.

Probiotic yoghurt stimulates digestion and promotes the settlement of positive bacterial strains. This is the approximate advertising slogan of the manufacturer. A probiotic contains viable microbiological organisms and is added to numerous foods, preferably in yoghurts and mixed drinks. Such functional foods with alleged health benefits are controversial in food science circles. In addition to functional foods, there are also a number of medicines which are preferably added to lactic acid bacteria for the treatment of inflammatory bowel diseases. To date, there are conflicting statements and studies on the actual benefits of these functional and dietary foods. A new US study was able to find a part of the changes in the intestine and thus refuted some advertising messages from the manufacturer.

According to an international scientific study, the effects of probiotics are different than previously thought. Neither the colonization of intestinal bacteria nor the composition of the intestinal flora is altered by probiotic foods. Researchers at the Washington University School of Medicine in St. Louis, however, found in their study that probiotics change the behavior of microbes in the gut. However, the research team was only able to observe this property as long as the subjects consumed daily probiotic yoghurt.

Enzymes are involved in metabolic pathways
The examined yogurts contained five different living bacterial cultures. During the seven-week study, study participants ate yoghurt with probiotics daily. During this time, the scientists investigated the metabolic activities as well as the effects on the human intestinal flora. To ensure the results, mice were also given probiotics. The subsequent analysis showed that the probiotics significantly altered the activities of the intestinal flora in humans as well as in the animals. The microbes in the intestine produced some more enzymes. Others, however, were less stimulated or even showed less activity in the comparison subjects without probiotic supplements in yogurt. „These enzymes are involved in numerous metabolic pathways, including carbohydrate processing“, Study author Nathan McNulty reports.

Study provided first starting point
Previous studies have shown that probiotics provide relief for intestinal inflammation and diarrhea. The evaluations of the scientists could now explain why this is the case, explained McNulty. It is still unclear, however, which health effects could be triggered by the altered intestinal flora. How the probiotic strains produce this effectivation is still unknown. However, the study should provide initial starting points, as the researchers emphasized.

To uncover the effects of subtle bacteria, scientists used two experimental setups. In the first setup, seven identical twins took part. One sibling drank a probiotic drink, others did not take a probiotic. The preparation contained in addition to lactobacilli of the genera Bifidobacterium and Lactobacillus additionally three probiotic bacterial species. Producers of drink promote with arguments that drugs preserve prophylactically against bacterial and viral infectious diseases and protect against allergies. In addition, the drink is supposed to strengthen the immune system. At the end of the study, stool specimens showed that two of the bacterial strains Streptococcus thermophilus and Lactobacillus delbrueckii did not survive in the first intestinal passage. The other two species made their way into the intestine, but had no way to settle.

In a second round, the scientists vaccinated germ-free mice 15 human intestinal bacterial strains. Beforehand, genes and metabolic products of the strains were precisely mapped. Through this experiment, the scientists were able to detect changes and deviations in the metabolic schema recognizable and unerring in human study participants identical pattern movements. This made it possible to identify a total of 86 changes in the production of enzymes in the human intestinal flora. (Sb)

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Image: Michael Hirschka